Dietary Lipid Levels Research Articles

Effect of dietary lipid levels on growth, body composition, and enzyme activities of larvae of butter catfish, Ompok bimaculatus (Actinopterygii: Siluriformes: Siluridae)

The Indian butter catfish, Ompok bimaculatus (Bloch, 1794), is a high-value catfish that has gained immense consumer preference in South-East Asia. However, information on the nutritional requirements of this species is scanty. Hence, an experiment was conducted to evaluate the effects of varying dietary lipid levels on growth, body composition, and activities of digestive and metabolic enzymes in larvae. Three isonitrogenous (40% crude protein) diets were formulated by supplementing fish and vegetable oil (1:1) at 4.5% (D1), 7% (D2), and 9.5% (D3) levels (containing crude lipid 5.7%, 8.0%, and 10.45%, respectively in diets D1–D3) to a fish meal- and oilcake-based formulated diet. Experimental diets were fed to butter catfish larvae (0.15 ± 0.01 g) in triplicate groups for a period of 42 days. Proximate compositions of the experimental diets, as well as fish carcass, were analyzed using standard procedures (AOAC 2005). Digestive and metabolic enzyme activities were analyzed at the completion of the experiment by standard methodology. Butter catfish larvae fed the diet D2 (8% crude lipid) resulted in the best performance in terms of weight gain (final weight 1.40 ± 0.07 g), net weight gain (1.31 ± 0.06 g), specific growth rate (5.50 ± 0.05% · day−1), and protein efficiency ratio (2.39 ± 0.17). The highest lipid deposition (2.90 ± 0.12%) in the carcass was also recorded in fish reared on diet D2. The final weight, net weight gain, protein efficiency ratio, and specific growth rate were significantly (P < 0.05) higher in D2 having 8% lipid. Moisture and lipid contents of the whole body were significantly (P < 0.05) higher in larvae fed diet D2. Amylase activity in fish significantly (P < 0.05) decreased with increasing dietary lipid levels. The maximum alkaline protease, pepsin, and lipase activities were noticed in the larvae fed diet D2. Progressive decrease in liver glucose-6-phosphate dehydrogenase activities and significant increase (P < 0.05) in the activities of neoglucogenic enzymes (glucose-6-phosphatase and fructose-1,6-bis phosphatase) were noticed with an increase in dietary lipid levels. Significantly lower (P < 0.05) activities of LDH, ALT, and AST were recorded in the group fed diet D2. Results of the study indicated that 8% crude lipid in the diet could assure optimum growth and survival of butter catfish larvae during early development. An appraisal on growth, body composition, and digestive as well as metabolic function in the butter catfish larvae recorded in the study might provide some important information to consider application of formulated diets for the larviculture of Ompok bimaculatus.

Effect of dietary lipid levels on growth, body composition, and enzyme activities of larvae of butter catfish, Ompok bimaculatus (Actinopterygii: Siluriformes: Siluridae)

The Indian butter catfish, Ompok bimaculatus (Bloch, 1794), is a high-value catfish that has gained immense consumer preference in South-East Asia. However, information on the nutritional requirements of this species is scanty. Hence, an experiment was conducted to evaluate the effects of varying dietary lipid levels on growth, body composition, and activities of digestive and metabolic enzymes in larvae. Three isonitrogenous (40% crude protein) diets were formulated by supplementing fish and vegetable oil (1:1) at 4.5% (D1), 7% (D2), and 9.5% (D3) levels (containing crude lipid 5.7%, 8.0%, and 10.45%, respectively in diets D1–D3) to a fish meal- and oilcake-based formulated diet. Experimental diets were fed to butter catfish larvae (0.15 ± 0.01 g) in triplicate groups for a period of 42 days. Proximate compositions of the experimental diets, as well as fish carcass, were analyzed using standard procedures (AOAC 2005). Digestive and metabolic enzyme activities were analyzed at the completion of the experiment by standard methodology. Butter catfish larvae fed the diet D2 (8% crude lipid) resulted in the best performance in terms of weight gain (final weight 1.40 ± 0.07 g), net weight gain (1.31 ± 0.06 g), specific growth rate (5.50 ± 0.05% · day−1), and protein efficiency ratio (2.39 ± 0.17). The highest lipid deposition (2.90 ± 0.12%) in the carcass was also recorded in fish reared on diet D2. The final weight, net weight gain, protein efficiency ratio, and specific growth rate were significantly (P < 0.05) higher in D2 having 8% lipid. Moisture and lipid contents of the whole body were significantly (P < 0.05) higher in larvae fed diet D2. Amylase activity in fish significantly (P < 0.05) decreased with increasing dietary lipid levels. The maximum alkaline protease, pepsin, and lipase activities were noticed in the larvae fed diet D2. Progressive decrease in liver glucose-6-phosphate dehydrogenase activities and significant increase (P < 0.05) in the activities of neoglucogenic enzymes (glucose-6-phosphatase and fructose-1,6-bis phosphatase) were noticed with an increase in dietary lipid levels. Significantly lower (P < 0.05) activities of LDH, ALT, and AST were recorded in the group fed diet D2. Results of the study indicated that 8% crude lipid in the diet could assure optimum growth and survival of butter catfish larvae during early development. An appraisal on growth, body composition, and digestive as well as metabolic function in the butter catfish larvae recorded in the study might provide some important information to consider application of formulated diets for the larviculture of Ompok bimaculatus.

Screening of reference genes in tiger puffer (Takifugu rubripes) across tissues and under different nutritional conditions.

The present study was aimed at screening suitable reference genes for quantitative real-time polymerase chain reaction (qRT-PCR) in tiger puffer (Takifugu rubripes), an important aquaculture species in Asia and also a good model species for lipid research. Specifically, this reference gene screening was targeted at standardization of gene expression in different tissues (liver, muscle, brain, intestine, heart, eye, skin, and spleen) or under different nutritional conditions (starvation and different dietary lipid levels). Eight candidate reference genes (ribosomal protein L19 and L13 (RPL19 and RPL13), elongation factor-1 alpha (EF1α), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), hypoxanthine guanine phosphoribosyl transferase1 (HPRT1), beta-2-Microglobulin (B2M), 18S ribosomal RNA (18SrRNA), and beta actin (ACTB)) were evaluated with four algorithms (geNorm, NormFinder, BestKeeper, and comparative ΔCt method). The results showed that different algorithms generated inconsistent results. Based on these findings, RPL19, EF1α, 18SrRNA, and RPL13 were relatively stable in different tissues of tiger puffer. During starvation conditions, ACTB/RPL19 was the best reference gene combination. Under different dietary lipid levels, ACTB/RPL13 was the most suitable reference gene combination. The present results will help researchers to obtain more accurate results in future qRT-PCR analysis in tiger puffer.

Dietary lipid levels affect growth, feed utilization, lipid deposition, health status and digestive enzyme activities of juvenile Siberian sturgeon, Acipenser baerii

A 10-week experiment was conducted to evaluate the effects of dietary lipid levels on growth, feed utilization, lipid deposition, health status and digestive enzyme activities of juvenile Siberian sturgeon (Acipenser baerii). Six isonitrogenous diets were formulated with lipid levels at 51.1 (L5), 88.7 (L9), 129.6 (L13), 169.3 (L17), 208.4 (L21) and 248.8 g/kg (L25). The sturgeons fed with L17 had the highest growth and feed utilization. Higher dietary lipid obtained significantly lower PPV than that of L17 (p < .05). Based on WGR, PPV, the optimal dietary lipid was estimated at 169.9, 176.0 g/kg. The lipid deposition in the whole body, muscle and liver enhanced significantly as the dietary lipid increased (p < .05). Dietary lipid levels affected serum biochemical parameters, with the highest AST, TC, LDL-C and LDL-C/TC in L21 or L25 group and highest HDL-C in the L17 group. Serum antioxidants, oxidants and liver MDA content maintained upward trends with increasing dietary lipid from 51.1 to 248.8 g/kg (p < .05). Lipase activity in the spiral valve intestine increased when dietary lipid rose from 51.1 to 169.3 g/kg, but declined when lipid level up to 208.4 and 248.8 g/kg (p > .05). To sum up, the optimal dietary lipid was 169.9–176.0 g/kg for juvenile Acipenser baerii.

Effects of graded dietary lipid levels on growth, feed utilization, body composition and metabolism in juvenile white leg shrimp, Penaeus vannamei (Boone, 1931) reared in inland saline water of 10 g/L salinity

A feeding trial was performed for 60 days to determine the dietary lipid requirement of Penaeus vannamei juveniles reared in inland saline water (ISW) of 10 g/L salinity. Six iso-nitrogenous (360 g/kg crude protein) and heterocaloric (15.4–17.6 KJ DE/g) semi-purified diets were prepared with graded level of lipid viz., 20, 40, 60, 80, 100 and 120 g/kg (L2–L12 with 20 g/kg incremental level). Two hundred and seventy P. vannamei juveniles (5.51 ± 0.01 g) were randomly allocated (15 shrimps/200 L) into six treatment groups in triplicate following a completely randomized design. The shrimp of L4 and L6 groups exhibited significantly higher per cent weight gain (WG%), specific growth rate and protein efficiency ratio and the lowest feed conversion ratio. The lipid efficiency ratio and hepatopancreatic somatic index were significantly decreased and increased with increasing levels of lipid respectively. The L6, L8 and L10 groups exhibited significantly higher (p < .05) lipase activity. Shrimp of higher dietary lipid fed groups exhibited significantly higher (p < .05) aminotransferase activity than their lower dietary lipid fed counterparts. Based on WG% data, broken-line linear and second-order polynomial regression analysis showed that the optimal dietary lipid requirement of P. vannamei in ISW of 10 g/L salinity was 46.5 and 51.4 g/kg respectively.

Interactive effects of dietary lipid and nutritional emulsifier supplementation on growth, chemical composition, immune response and lipid metabolism of juvenile Nile tilapia (Oreochromis niloticus)

The objective of this study was to investigate the interactive effects of supplementation with different levels of dietary lipids and a commercial nutritional emulsifier (NE) on the growth, feed utilization, immune response and lipid metabolism of juvenile Nile tilapia (Oreochromis niloticus). A 5 × 2 factorial design was formulated with five lipid supplement levels (0, 15, 30, 45 and 60 g/kg) and NE supplementation (with or without NE at 0.35 g/kg). Nile tilapia with an initial average body weight of 8.06 g were randomly placed in 30 cages and offered one of the ten diets for 8 weeks. The results show that dietary NE supplementation significantly increased the final weight, weight gain and specific growth rate compared with fish fed diets without NE (P<0.05). Interestingly, dietary NE supplementation significantly improved the feed conversion ratio (P<0.05). The supplementation of diets with NE significantly reduced the cholesterol levels (P<0.05). The activities of catalase, superoxide dismutase and glutathione peroxidase significantly decreased as dietary lipid supplement levels increased, but they were significantly improved by dietary NE supplementation (P<0.05). The results also show that the liver malondialdehyde (MDA) content significantly increased as lipid supplement levels increased, while NE supplementation resulted in significantly decreased MDA levels (P<0.05). As dietary lipid supplement levels increased, the crude lipid content of the fillet significantly increased in fish fed a diet supplemented with NE (P<0.05). Moreover, lipase activity was significantly increased when the diet was supplemented with NE (P<0.05). A total of 20 fatty acids were measured in the fillets of fish fed diets supplemented with different lipid levels and NE. Significantly higher levels of polyunsaturated fatty acids, particularly linoleic acid (18:2 n6c), γ-linolenic acid (C18:3 n6) and α-linolenic acid (C18:3 n3), were found in fish fed diets supplemented with NE. In summary, dietary NE supplementation has a positive effect on feed digestion and absorption, resulting in improved fish growth performance, immune response and nutritional value of the muscle due to increased essential fatty acid contents. NE supplementation is particularly effective when it is added to diets with low lipid levels.

Effects of Dietary Protein and Lipid Levels on Growth, Body Composition, Blood Biochemistry, Antioxidant Capacity and Ammonia Excretion of European Grayling (Thymallus thymallus)

This study evaluated growth, body composition, antioxidant capacity, innate immunity and ammonia excretion of European grayling (Thymallus thymallus) fed diets containing different protein and lipid contents. Six diets were produced to contain 30, 40, or 50% protein and 10 or 20% lipid. Juvenile fish averaging 25.2 ± 0.28 g were stocked into eighteen 450-L circular tanks in a recirculating aquaculture system (RAS) and fed the test diets to satiation twice daily for 12 weeks. Fish weight gain (WG) was enhanced (P &amp;lt; 0.05) as dietary protein increased from 30% (229% WG) to 40% (262% WG) and plateaued thereafter. Enhancing protein and lipid content of diet led to reduced feed intake. Also, feed efficiency was improved by increasing dietary protein (by 40.8%) and lipid (by 16.5%) levels. An interaction of protein and lipid was found on whole-body lipid, and muscle lipid content increased as dietary lipid level increased. Muscle arachidonic acid (ARA), eicosapentaenoic acid (EPA, 20:5n-3) and total n-6 long-chain polyunsaturated fatty acids (LC-PUFA) contents enhanced by increasing dietary protein level. Moreover, increasing fat content of diet led to enhanced muscle linoleic acid, linolenic acid, total monounsaturated fatty acids (MUFA), total n-6, ratio of docosahexaenoic acid (DHA, 22:6n-3) to EPA and n-6/n-3. However, EPA, DHA, total n-6 LC-PUFA, total n-3, total n-3 LC-PUFA, and EPA/ARA ratio decreased at higher dietary lipid level. Serum triglyceride (TG) level and lactate dehydrogenase (LDH) activity decreased as dietary protein level increased. Increasing fat content of diet led to enhanced serum TG, cholesterol and glucose concentrations and reduced alanine aminotransferase, aspartate amino transferase and LDH activities. Serum malondialdehyde concentration was enhanced by increasing both dietary protein and lipid. Furthermore, serum myeloperoxidase activity was enhanced at higher dietary lipid level. Water ammonium nitrogen (NH4+-N) concentration was measured after 5 and 24 h of last feeding, and the results indicated the reduction of ammonia excretion as dietary lipid content increased. These findings suggest that 40% dietary protein can support optimal growth of juvenile European grayling reared in RAS and increasing lipid content from 10 to 20% can improve feed utilization and reduce ammonia excretion to the rearing water.

Effect of dietary lipid levels on growth performance, body composition, and feed utilization of juvenile spotted knifejaw Oplegnathus punctatus

An 8-week feeding trial was carried out with various lipid level (2.30 %, 6.31 %, 8.98 %, 12.93 %, 16.08 %, and 18.99 %) diets to investigate the effects on growth performance, body composition, and feed utilization of juvenile spotted knifejaw Oplegnathus punctatus. After the feeding experiment, the weight gain (WG) and specific growth rate (SGR) significantly elevated with raising the dietary lipid level to 12.93 %, and then decreased when dietary lipid further increased (p < 0.05). The tendencies of feed efficiency (FE), protein efficiency ratio (PER), nitrogen retention (NR), and energy retention (ER) were consistent with the growth performance (p < 0.05). The lipid retention (LR) significantly decreased with dietary lipid increasing (p < 0.05). The fish consuming 2.30 % and 6.31 % lipid diets had significantly elevated hepatosomatic index (HSI) (p < 0.05). The intraperitoneal fat ratio (IPF) increased with the increase of dietary lipid levels (p < 0.05). The elevation of dietary lipid levels significantly increased the lipid concentrations in the whole body, dorsal muscle, and liver (p < 0.05). The highest liver glycogen deposition was found in the 2.30 % dietary lipid treatment (p < 0.05). The fish fed the diets added with 12.93 % lipid diet had the highest serum protein concentration (p < 0.05). The lowest total cholesterol (TC) content in the serum was detected in 2.30 % dietary lipid treatment (p < 0.05). The fish fed diets with 2.30 % or 18.99 % lipid obtained elevated serum AST and ALT activities (p < 0.05). The regression analysis in second order polynomial and two slope broken-line mode based on SGR and FE indicated that diet containing 10.46–12.83 % lipids was optimal for juvenile O. punctatus to obtain best growth performance and feed efficiency.

Impacts of dietary konjac glucomannan supplementation on growth, antioxidant capacity, hepatic lipid metabolism and inflammatory response in golden pompano (Trachinotus ovatus) fed a high fat diet

This study examined the effect of konjac glucomannan (KGM) supplementation in diets with different lipid levels on growth, antioxidant capacity, hepatic lipid metabolism and inflammatory response in juvenile pompano (Trachinotus ovatus). Triplicate groups of fish (12.07 ± 0.21 g) were fed eight experimental diets containing two lipid levels of 9% (basal-fat diet, BFD) and 18% (high-fat diet, HFD), and four levels of KGM (0, 0.5, 1 and 2%) for 60 days. Pompano fed HFD exhibited markedly lower growth and feed efficiency than fish fed BFD, and KGM supplementation, particularly at 1% inclusion, significantly improved growth performance and feed efficiency in fish fed both BFD and HFD. In addition, Pompano fed HFD showed higher whole-body lipid and lower protein contents than fish fed BFD. Irrespective of dietary lipid level, whole body, dorsal and ventral muscle were reduced by dietary KGM supplementation up to 1% while the opposite was found for whole body protein content. Dietary KGM also significantly reduced the HSI, liver lipid contents, as well as lipid droplets in the liver. Supplementation of KGM to both BFD and HFD significantly reduced serum total cholesterol, triglyceride, low-density lipoprotein cholesterol and free fatty acids levels. Furthermore, irrespective of dietary lipid level, increasing dietary KGM supplementation enhanced serum IgM level, lysozyme and alkaline phosphatase activities, and reduced serum alanine aminotransferase and aspartate aminotransferase activities. Dietary KGM also increased liver total antioxidant capacity, superoxide dismutase and catalase activities, and decreased malondialdehyde concentration in fish fed both HFD and BFD. Dietary KGM significantly increased serum glutathione peroxidase, superoxide dismutase and catalase activities and reduced malondialdehyde concentrations in fish fed BFD, and enhanced serum total antioxidant capacity and glutathione peroxidase activity in fish fed HFD. Supplementation of KGM increased the expression of genes associated with lipid catabolism (pparα, cpt1, hsl) and lipid transport (fabp1, apoB100 and cd36), and decreased the expression of lipid anabolism related genes (srebp1, pparγ, fas and acc). Moreover, the expression of pro-inflammatory cytokines including tumor necrosis factor α and interleukin-8 were down-regulated, while expression of the anti-inflammatory cytokine transforming growth factor β1 was increased by KGM supplementation. In conclusion, supplementation of KGM at 1% of diet improved growth, feed efficiency, antioxidant capacity, hepatic lipid metabolism and inflammatory responses in juvenile pompano, and can mitigate excessive deposition of lipid in tissues of farmed fish.

Excessive Dietary Lipid Affecting Growth Performance, Feed Utilization, Lipid Deposition, and Hepatopancreas Lipometabolism of Large-Sized Common Carp (Cyprinus carpio).

An 82-day study was conducted to assess the effect of the dietary lipid levels on growth performance, feed utilization, lipid deposition, and hepatopancreas lipometabolism of large-sized common carp (Cyprinus carpio). Six isonitrogenous (300 g/kg protein) pelletized diets with different dietary lipid levels (30, 60, 90, 120, 150, and 180 g/kg) were fed in triplicate to fish groups with 75 individuals (with an initial mean weight of 247.00 ± 16.67 g). The results showed that there was a significant increase in weight gain (WG) rate (WGR), specific growth rate (SGR), and protein efficiency ratio (PER) as dietary lipid levels increased from 30 to 60 g/kg (p < 0.05) and then there was a decline. Feed conversion rate (FCR) was observed to be significantly lower in 60 g/kg lipid treatments (p < 0.05). Muscle crude protein contents were obtained to be significantly higher in 60 and 90 g/kg treatments (p < 0.05). The crude lipid content in the hepatopancreas increased significantly with an increase in dietary lipid levels (p < 0.05). The expression of lipoprotein lipase (LPL) and carnitine palmitoyltransferase-1 (CPT1) in the hepatopancreas was significantly downregulated with an increase in dietary lipid levels while the expression of growth hormone (GH), insulin-like growth factor-1 (IGF-1), fatty acid synthase (FAS), acetyl-CoA carboxylase-1 (ACC-1), and sterol regulatory element binding protein (SREBP) was upregulated first in 30 and 60 g/kg lipid treatments and then downregulated significantly in other treatments. The results revealed that excess dietary lipid supplements (more than 60 g/kg) would inhibit WG and would aggravate the lipid decomposition in the hepatopancreas. Based on WGR and FCR, the dietary lipid levels of 59.5 and 70.4 g/kg were optimal for growth performance and feed utilization of large-sized common carp.

Effects of different dietary lipid levels on intestinal mucosal barrier and microbial community of juvenile tiger puffer Takifugu rubripes

A 65-day feeding trial was conducted to investigate the effects of different levels of dietary lipid on intestinal health of tiger puffer. Three experimental diets were formulated, differing in lipid level, that is, 90.3 (control-suitable lipid, C-SL), 130.3 (moderately high lipid, MHL) and 170.3 (extremely high lipid, EHL) g/kg dry matter. The results showed that with increasing dietary lipid levels, the activities of total antioxidant capacity, Na+ K+-ATP, amylase and trypsin were significantly decreased by diets MHL and EHL. Compared with C-SL, the mRNA expression of the intestinal tight junction proteins (Claudin14, Claudin18, junctional adhesion molecule-A) were significantly down-regulated and the serum diamine oxidase enzyme activity was significantly increased in the EHL group. Diet EHL up-regulated the gene expression of the pro-inflammatory cytokines, tumour necrosis factor-α, interferon-2, interleukin (IL)-1β, IL-8 and IL-15, and down-regulated that of anti-inflammatory cytokine transforming growth factor -β. Sequencing of intestinal bacterial 16s rRNA V4 region showed that diet EHL significantly increased the Firmicutes/Bacteroidetes ratio, decreased the alpha diversity of intestinal microbiota and the relative abundance of some potential beneficial bacteria such as Lactobacillus, Sphingomonas and Thermus. These results showed that high level of dietary lipid (170.3 g/kg) had negative effects on function status, mucosal barrier and microbial communities of tiger puffer intestine, indicating that tiger puffer was sensitive to the dietary lipid level.

Effects of dietary lipid levels on growth performance, plasma biochemistry, lipid metabolism and intestinal microbiota of juvenile golden pompano ( Trachinotus ovatus )

Five isonitrogenous diets were formulated containing five graded levels of lipid (52.0, 81.0, 112.0, 141.0 and 171.0 g/kg). The diets were fed to triplicate groups of juvenile Trachinotus ovatus (10.49 ± 0.23 g) for 8 weeks. Results showed that moderate lipid level in diets significantly increased weight gain rate (WGR), specific growth rate (SGR) and feed efficiency rate (FER) (p < .05). The dietary lipid level affected plasma biochemical indexes containing total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-c), total lipase (TL) and non-esterified fatty acid (NEFA) significantly (p < .05). The dietary lipid level also had significant effects on enzymatic activities including alanine aminotransferase (ALT), aspartate aminotransferase (AST), total lipase (TL), fatty acid synthetase (FAS), intestinal lipase (ILPS), adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) (p < .05). The relative level of hepatic carnitine palmitoyltransferase I (cpt1) mRNA increased significantly with increasing dietary lipid levels. The mRNA level of hepatic fatty acid synthase (fas) was significantly upregulated with dietary lipid level up to 81.0 g/kg and then decreased (p < .05). Moreover, dietary lipid level influenced microbial community to regulate metabolic capacity of intestine. The optimum dietary lipid level for the optimal growth of juvenile Trachinotus ovatus was 93.6 g/kg.

Effects of dietary lipid levels on growth performance, hepatic health, lipid metabolism and intestinal microbiota on Trachinotus ovatus

Proper dietary lipid is beneficial for the protein-sparing effect and reduces feed budget. Therefore, 8 weeks trial feeding with different lipid levels diets was performed to determine the optimal supplement level through the investigation on growth performance, hepatic health, lipid metabolism and intestinal microbiota of Trachinotus ovatus. Six diets (D1 - D6) containing 90 g/kg, 120 g/kg, 150 g/kg, 180 g/kg, 210 g/kg and 240 g/kg lipid were formulated, respectively. Each diet was randomly assigned to four groups of fish (initial body weight 7.58 ± 0.10 g), and fish was fed twice daily to apparent satiation. Results showed that the weight gain and the specific growth rate of T. ovatus fed with D2 diet were significantly higher than the D1, D5 and D6 treatments (p < .05), and D2 treatment did not show a statistical difference with D3 and D4 treatments. Related antioxidant enzyme activities such as superoxide dismutase, as well as the RNA expression of antioxidant genes, such as glutathione reductase, showing a significant upward and then downward trend with the increase of dietary lipid, and D4 treatments reached the highest value. One of the intestinal microbiotas—Nocardiaceae, demonstrating a similar change trend to the antioxidant capacity of fish. Transaminase of serum and malondialdehyde of liver in D5 and D6 treatments significantly higher than D1 treatments (p < .05). Hepatic RNA expression of PPARα and CPT-I increased first and then decreased with the increase of lipid level, obtaining the highest value in D4 and D5 treatments respectively. In conclusion, dietary lipid from 120 g/kg to 180 kg/kg is beneficial for growth and health of T. ovatus.

Interaction Between Dietary Lipid Level and Seasonal Temperature Changes in Gilthead Sea Bream Sparus aurata: Effects on Growth, Fat Deposition, Plasma Biochemistry, Digestive Enzyme Activity, and Gut Bacterial Community

A 121-day feeding trial was undertaken to test the effects of two dietary lipid levels (16 and 21% L16, L21) in triplicated gilthead sea bream groups (initial weight: 67.5 g) reared at two different water temperatures (high, H 23°C and low, L 17°C) in the same recirculation system but exposed to a switch in temperature after 58 days. Fish kept at H were transferred to L (HL transition, autumn shift), and the fish kept at L were exposed to H (LH transition, summer shift), while continuing to receive the same diet to apparent satiation in each group. At the end of the trial, no significant diet effect on specific growth rate (SGR), feed intake (FI), and feed conversion rate (FCR) were detected in fish exposed to HL transition compared with those exposed to LH transition, while gross lipid efficiency (GLE) and lipid efficiency ratio (LER) were higher in L16. After temperature changes, L16 displayed higher SGR, FI, GLE, and LER, while mesenteric fat index was reduced. After temperature changes, the combined effects of low lipid diet and low temperature conditions resulted in higher pepsin activity, while trypsin, chymotrypsin, and lipase activities were generally higher at high lipid content. The combined effect of diet and temperature did not alter the metabolic plasma profile, except for the observed final higher aspartate aminotransferase (AST) and alkaline phosphatase (ALP) values when combining high dietary lipid (L21) and temperature changes. Different diets showed a significantly different gut microbiome layout, only at high temperature with L16 diet resulting in a higher load of Lactobacillus. On the contrary, no dietary impact on ecosystem diversity was observed, independently from the temperature. In addition, L16 diet in the HL transition favored an increase in Weissella and Bradyrhizobium genera in the gut microbiome, while in the final condition of LH transition, L21 diet favored a significant increase in Streptococcus and Bacillus. According to the results, the utilization of 16% dietary lipid levels in gilthead sea bream should be preferred during seasonal temperature changes in order to optimize feed utilization and gut health.

Physiological and metabolic protein‐sparing effects of dietary lipids on common snookCentropomus undecimalis(Bloch, 1792) juveniles

Carnivorous common snook (Centropomus undecimalis) has potential for aquaculture, but its protein requirement in diet is 500 g kg−1 and the energetic role of lipids in this species has not been explored. Thus, this study investigated the ability of juvenile common snook (8.7 ± 1.2 g) to use dietary lipids as an energy source. The fish were fed four practical diets with two protein levels (400 and 500 g kg−1) associated with two lipid levels (60 and 120 g kg−1) for 12 weeks. Growth performance significantly improved with increasing dietary lipid levels, but no significant difference was observed at the protein level. Fish fed the 400:60 (protein: lipid level) diet exhibited significantly higher feed conversion ratios than those fed 400:120, 500:60 and 500:120 diets, but fish fed the 400:120 diet had significantly higher protein efficiency ratios. Juvenile common snook showed the ability to modulate digestive protease and lipase secretion when dietary protein or lipid levels were modified. The activity of alanine aminotransferase decreased as the dietary lipid level increased (p < .05), while fructose-1 and 6-bisphosphatase activities were not significantly affected by dietary protein or lipid levels. Glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and pyruvate kinase activities increased as dietary protein and lipid levels increased (p < .05). The results of this study indicate that an increase in dietary lipid level has a protein-sparing effect and that the diet containing 400 g kg−1 protein with 120 g kg−1 lipid is suitable for growth and effective protein utilization in common snook.

Evaluation of protein: lipid ratio on growth, feed efficiency, and metabolic response in juvenile yellowtail snapper Ocyurus chrysurus (Bloch, 1791)

This study was conducted to evaluate juveniles' Ocyurus chrysurus (13.7 ± 0.45 g initial weight) to utilize lipid as an energy source on growth, feed efficiency, body composition, digestive and hepatic enzyme activities. Four diets of two protein levels (40 and 50%) with two lipid levels (6 and 12%) and 2% of digestible carbohydrates were formulated. Fish were fed for 60 days to apparent satiation at a stocking density of 10 fish per tank (100 L). Growth gain of fish fed 50% dietary protein was higher than of fish fed 40% dietary protein (P &lt; 0.05). However, feed efficiency was significantly higher at 12 than 6% of dietary lipid. Whole-body lipid and glycogen in the liver increased dramatically with dietary lipid content-alkaline protease activity trend increased as dietary protein increased. Trypsin activity increased significantly as dietary lipid decreased, whereas chymotrypsin activity showed the opposite trend (P &lt; 0.05). Bile salt-dependent lipase activity trend towards increasing as dietary energy decreased. Glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH), and fructose-1, 6-biphosphatase (FBPase) significantly increased with increasing dietary lipid levels. However, alanine aminotransferase (ALT) activity increased with dietary protein content. On the other side, pyruvate kinase (PK) activity increased with both dietary protein and lipid content. This study indicates that high dietary lipid (12%) improved the feed efficiency but did not reduce dietary protein demand in juveniles O. chrysurus.

The optimal dietary protein and lipid levels for juvenile hybrid sunfish ( lepomis cyanellus ♀ × Lepomis macrochirus ♂)

An eight-week feeding trial was conducted to examine the optimal dietary protein and lipid levels for juvenile hybrid sunfish (Lepomis cyanellus ♀ × Lepomis macrochirus ♂). A 5 × 2 factorial layout containing five protein levels (300, 340, 380, 420 and 460 g kg−1) and two lipid levels (30 and 80 g kg−1) was designed. Fish (initial body weight 1.21 ± 0.06 g) were fed the test diets twice daily. The final body weight (FBW) and per cent weight gain (PWG) in fish increased with dietary protein level from 300 to 420 g kg−1, and afterwards decreased with dietary protein level from 420 to 460 g kg−1. Feed intake and feed conversion ratio (FCR) significantly declined with increase dietary protein level. Fish fed at 380 and 420 g kg−1 dietary protein level exhibited higher nitrogen retention efficiency (NRE) and phosphorus retention efficiency (PRE), however, lower nitrogen and phosphorus wastes, than in fish fed at 300 g kg−1 dietary protein level. For different dietary lipid levels, the higher FBW, PWG, NRE and PRE, but the lower feed intake, FCR, nitrogen and phosphorus wastes, were found in fish fed at 80 g kg−1 dietary lipid level than those in fish fed at 30 g kg−1 dietary lipid level. At the end of feeding trail, the contents of body moisture and lipid were significantly influenced by dietary lipid level. According to these results, a diet containing 420 g kg−1 protein and 80 g kg−1 lipid is recommended for efficient growth of juvenile hybrid sunfish.

Optimal dietary lipid requirement for juvenile Asian red-tailed catfish (Hemibagrus wyckioides): Dietary lipid level for Hemibagrus wyckioides

This study investigated the effects of dietary lipid content on growth rate, feed utilization, digestive enzyme activity, and antioxidant capacity of juvenile Asian red-tailed catfish (Hemibagrus wyckioides), and thereby to evaluate the optimal dietary lipid requirement. Five isoproteic diets were prepared to contain varied levels of dietary lipid (3 %, 5.5 %, 8 %, 10.5 %, and 13 %). Each diet was fed to triplicate groups of juveniles (average body weight 3.20 g) in a recirculating farming system maintained at 28 ± 1 °C. Daily gain coefficient (DGC) and protein efficiency ratio improved steadily with the dietary lipid content up to 10.5 %, and then reached a plateau. Similarly, protein retention increased gradually with the dietary lipid content up to 13 %. Conversely, lipid retention decreased linearly with increasing dietary lipid content, but no significant difference was found among juveniles fed diets with 8 %, 10.5 %, and 13 % lipid. The optimum feed conversion ratio (FCR) was observed in juveniles fed diets with 10.5 % or 13 % lipid. Plasma insulin-like growth factor 1 level increased steadily with the dietary lipid content up to 8 %. However, plasma amino methyl propanediol, aspartate aminotransferase and alanine aminotransferase activities depressed generally with increasing dietary lipid content. Besides, the highest hepatic peroxidase, catalase, glutathione peroxidase, and alkaline phosphatase activities were found in juveniles fed diet with 10.5 % lipid. Single-slope broken-line regression analysis of DGC or FCR response to varied levels of dietary lipid showed that the optimal dietary lipid requirement of juvenile H. wyckioides was 11.1 % or 9.4 % of diet containing 42 % protein, respectively.

The optimal dietary lipid level for golden pompano Trachinotus ovatus fed the diets with fish meal replaced by soy protein concentrate

A feeding trial was conducted to determine the optimal dietary lipid level for golden pompano Trachinotus ovatus and the effect of dietary lipid level on fish meal replacement with soy protein concentrate (SPC). Eight isonitrogenous diets were formulated to contain four lipid levels (65 g/kg, 85 g/kg, 105 g/kg and 125 g/kg) and two fish meal levels (280 g/kg and 140 g/kg) respectively. Fish (initial weight 25.2 ± 0.5 g) were fed the test diets in net pens for 7 weeks. At the same dietary fish meal level, weight gain and nitrogen retention efficiency (NRE) tended to increase, while feed intake, feed conversion ratio (FCR) and nitrogen waste tended to decrease, with elevating dietary lipid level from 65 g/kg to 105 g/kg. At the same dietary lipid level, no significant differences were found in weight gain, feed intake, FCR, NRE, condition factor, hepatosomatic index, proximate composition and nitrogen waste between fish fed the diets containing 280 g/kg and 140 g/kg fish meal. This study reveals that the optimal dietary lipid level for golden pompano should be 107 g/kg, and dietary fish meal level could be reduced to 140 g/kg by using SPC as a fish meal substitute. Elevating dietary lipid level could not significantly increase fish meal replacement level with SPC.

Are the effects of dietary lipid content in grazing beef cattle independent of the amount of concentrate supplement?

This study aimed to evaluate the effects of levels of concentrate supplement and dietary lipids on the nutritional characteristics, metabolic parameters, and performance of Nellore bulls grazing tropical pasture. Twenty-seven Nellore bulls were allotted to 2 × 2 completely randomized factorial design with two levels of supplementation and two levels of dietary lipids. The concentrate supplement was fed at 4 g kg-1 BW (low supplementation) and 8 g kg-1 BW (high supplementation), whereas the dietary lipid content was 28 g of ether extract (EE) g-1 on a dry matter basis (DM) (low-lipid diet) and 42 g EE kg-1 DM (high-lipid diet). There was no interaction between the level of concentrate supplement and dietary lipid content on all studied variables. High levels of supplementation led to shorter grazing time and reduced forage dry matter intake (DMF). On the other hand, the DM intake increased with increasing levels of concentrate supplement, with no significant effects on DM digestibility. The dietary lipid content did not affect forage and DM intakes. However, the digestibility of DM and neutral detergent fiber (NDF) were lowest in high-lipid diets. Bulls receiving high levels of supplementation had higher average daily gains than low-supplemented animals. Neither the amount of concentrate supplement nor the dietary lipid content affected the hot carcass yield and carcass weight. Carcass fat deposition was greater in bulls fed high-lipid diets than in animals receiving low-lipid diets. The effects of the level of concentrate supplement and dietary lipid content on the nutritional characteristics and performance of grazing beef cattle are independent. Concentrate supplementation at 8 g kg-1 BW increases cattle performance but decreases forage utilization. Diets containing 42 g EE kg-1 DM reduces the digestibility of dry matter and fiber fractions, but increases backfat thickness.